1. Field of the Invention
The present invention relates to a spacer screw having a first thread section which can be screwed into a base element, a head section with a free screw head-shaped end section an anchoring section having coaxially arranged ring-like projections, a shank section between the head section and the first thread section, and a recess for the insertion of a tool at the end face.
2. Description of the Prior Art
A spacer screw of this kind is known from U.S. Pat. No. 4,808,051. The screw is a countersunk screw with constant core diameter. The screw has a thread section at the front end, an anchoring section and a shank section arranged between them. The anchoring section comprises a plurality of ring-like projections which broaden in the direction towards the screw head. This screw is used to secure a construction element to a base element.
It has proved to be a disadvantage that this screw only has a restricted field of use. On screwing the thread section into the base element the force which has to be applied must be so large that the anchoring section is driven into the construction element. From that it follows that the construction element must always have a lower strength than the base element.
In another known embodiment the spacer screw has a first thread section at the front end, a second thicker thread section at the rear end and a shank section connecting the thread sections.
This screw has the disadvantages that the desired spacing between the base element and the construction element must previously be determined by spacers, because the correction of the spacing means that the screw is turned out of the construction element on being unscrewed because of the same thread pitch of the thread sections, and that the construction element can be pulled off from the thicker thread section as a result of the lack of a screw head, in particular with soft types of wood.
The invention is based on the object of providing a spacer screw which is not subjected to the above-named restrictions.